This application is based upon and claims priority to German Patent Application 199 53 463.2 filed Nov. 5, 1999, and German Patent Application 100 37 041.1 filed Jul. 27, 2000, which applications are herein expressly incorporated by reference.
The invention relates to a protective device for a drive assembly. The drive assembly includes a double universal joint with a double yoke, a first joint yoke, a second joint yoke and a first and a second cross member. The cross members articulatably connect the first joint yoke and the second joint yoke to a first and a second yoke associated with the double yoke.
DE 30 33 850 A1 describes a protective device for a double universal joint. A protective cone is connected to bearing means supported on a joint yoke. A tubular protective element is supported on the double yoke by a bearing race. In the non-articulated condition of the joint, the protective cone covers part of the length of the tubular protective element. Both components are connected to one another by friction locking, form-fitting or connecting means. Thus, in the direction of rotation, a permanent relative movement relative to one another is avoided. However, the existing protective assembly only allows the double universal joint to be partially covered in the axial direction if easy access to the components of the double universal joint is desired.
DE-OS 20 46 236 describes a protective device for a double universal joint. The protective device includes a protective dish associated with the first joint yoke. The protective dish extends over one end of a protective element which is rotatably movably supported on the inner double yoke. The protective element covers those partial regions of the double yoke which are positioned to one side of the bearing. The protecting portion of the protective element faces away from the protective dish and projects into a protective cone. A gap occurs between the elements of the protective device when the double universal joint is articulated. The gap enables engagement from the outside. Equally, when loads generated by external forces are applied, there is no adequate resistance because the protective elements are each open on one side and can thus be deformed. In consequence, there is a possibility of contact with the rotating components of the double universal joint. This contact may result in damage to the components. Thus, the protective function to prevent contact is no longer ensured.
DE 195 41 512 C1 describes a protective device for a driveshaft. The device has two single universal joints which are connected to one another in a rotationally fast way by two profiled tubes inserted into one another. The assembly is covered by the protective device. The protective device has two protective tubes enclosing the profiled tubes and protective cones connected to their ends by means of an attaching cap. The protective cones include folds. In order to ensure the radial stability of the protective cone, even if the latter is of the soft type, a supporting ring is provided which supports the protective cone at a distance from its fixing means on the inside of the attaching cap.
EP 0969218 A1 describes a protective device for a drive assembly with a double universal joint. Here, the protective cone includes folds and is secured by its first axial end to a bearing assembly of a driveshaft. Its second axial end has a fixing portion connected to a guiding ring. The guiding ring, via its inner end, projects into that part of the protective cone which is provided with folds. The guiding ring, in turn, via a cylindrical bore, is supported on an externally spherical bearing race which is supported on the inner double yoke of the double universal joint. As a result, a relative axial movement is permitted between the guiding ring and the bearing race. However, it has been found that this kind of support does not provide the required articulation ability. Accordingly, in view of the inadequately defined conditions of movement carried out by the protective cone with its folds and the guiding ring attached thereto relative to the bearing race, the amount of wear increases. In particular, wear occurs in the region of contact between the cylindrical bore of the guiding ring and the spherical outer face of the bearing race. In practical terms, a line contact exists. However, the advantage of this assembly is that a relatively long protective cone region exists with the folds. This leads to the ability to accommodate larger articulation angles.
It is an object of the present invention to provide a protective device for a drive assembly having a double universal joint. The protective device covers the rotating parts of the double universal joint. The protective device covers the rotating parts of the double universal joint and enables easy access to the double universal joint for maintenance work, while featuring a long service life.
In accordance with the invention, a protective device includes a plastic protective cone with a first axial end, a second axial end and folds therebetween. The protective device, at least in the axial direction, enables elastic deformation. The first axial end of the protective cone serves to be releasably connected to a bearing assembly at the first joint yoke. The second axial end serves as a fixing portion. A bearing race is rotatably supported around a rotational axis at the double yoke. The bearing race is positioned in the protective cone and includes a spherical outer bearing face. A guiding ring has an inner bearing face in the form of a hollow-spherical zone. The guiding ring has a first opening facing the first axial end and a second opening facing away from the first opening. The second opening has an opening cross-section which, at its maximum, corresponds to the sphere diameter of the inner bearing face. The first opening has a diameter which is smaller relative to the second opening. The first opening is further offset from the center of the hollow-spherical-zone-like inner bearing face towards the first axial end than the second opening. The second opening is either positioned in a plane containing the center of the inner bearing face or is also offset therefrom towards the first axial end. The guiding ring is connected to the second axial end of the protective cone. The protective cone, via the folds of the protective cone and its inner bearing face, is held so as to be pre-tensioned into contact with the outer bearing face of the bearing race.
The protective device is complemented by the protective dish which is usually provided at the tractor or at the implement. The protective device partially projects into the dish. The advantage of this inventive design is that, under articulation, the calotte-like support provided for the guiding ring ensures clearly defined conditions of movement for the protective cone with its region provided with folds. Furthermore, clearly defined conditions of movement for the guiding ring exists relative to the bearing race in the sense of a spatial movement of the spherical or hollow-spherical faces. This is due to the fact that the faces are always in contact with one another as a result of being loaded by the folds of the plastic convoluted boot. In addition, a surface contact is achieved which clearly reduces the amount of wear and results in a correspondingly long service life of the protective device. It is possible to achieve a long length provided with folds so that even if one takes into account the spatial movement which the guiding ring is able to carry out relative to the bearing race, large articulation angles are possible. As a result of the pre-tension, that part of the protective cone which is provided with folds is sufficiently supported, thus ensuring a high degree of radial stability.
Furthermore, access to individual components, a lubricating nipple for lubricating the centering means or the cross member bearings of the double universal joint, is provided by release or displacement at the first axial end of the protective cone in the region of the bearing means. Further, the bearing race and the guiding ring enable an assembly which provide extensive cover towards the second joint yoke. Thus, between the first axial end and the second axial end, a long length is obtained which can be provided with folds. Such a length with folds also enables large articulation angles. The angles, in the case of such joints, cover a range up to 80xc2x0. The deformation behavior of the protective cone is advantageously affected by the spatial movability of the guiding ring (spherical bearing). Overall, a largely closed cover is provided so that any interference from the outside is prohibited.
According to a further embodiment of the invention, the guiding ring towards the second axial end, in its region adjoining the second opening, includes a hollow-cylindrical or widening portion whose diameter is at least as great as the sphere diameter of the inner bearing face. This measure makes it possible, from a design point, to provide extensive cover towards the second joint yoke.
According to one embodiment, the center of the outer bearing face and the inner bearing face are offset from the articulation center of the joint towards the first axial end. The joint includes the second joint yoke, the second yoke of the double yoke and the second cross member.
It is particularly advantageous if the center of the outer bearing face and the inner bearing face are identical with the articulation center of the joint including the second joint yoke, the second yoke of the double yoke and the second cross member. This measure enables pivoting around a common center.
According to a further embodiment of the invention, the guiding ring is rotatable to a limited extent relative to the bearing race around the rotational axis. Thus, the guiding ring and the bearing race are jointly rotationally driven. Accordingly, a relative movement between the bearing race and the guiding ring is prevented in order to avoid any wear between the two components. Thus, the bearing race enables a relative movement of the double yoke. In order to ensure that the bearing race, the protective cone, and the remaining components of the protective device are stationary when the components received within the protective device rotate, the bearing race includes circumferentially distributed guiding grooves. The grooves extend parallel to the rotational axis and are engaged, in the direction of rotation with play, by the guiding ring, via correspondingly circumferentially distributed guiding cams extending parallel to the rotational axis. Because of the short axial length of the guiding cams, the movement of the guiding ring relative to the bearing race required for a particular angle of articulation can be carried out.
In the case of embodiments wherein small articulation angles are sufficient, the guiding ring has circumferentially distributed guiding grooves which extend parallel to the longitudinal axis. The guiding grooves are engaged, with rotational play, by correspondingly circumferentially distributed guiding wedges of the bearing race. The guiding wedges extend parallel to the rotational axis. The outer face of the guiding wedges are analogous to the spherical outer bearing face and include an outwardly extending curvature with a correspondingly increased diameter.
There are two embodiments with regard to the bearing race. First, the bearing race includes a portion by means of which it is directly supported on the double yoke. Second, the bearing race includes a basic member with a receiving bore and a slotted sliding ring. The sliding ring is secured in the receiving bore. As a result, it is possible to select a sliding ring material which has particularly advantageous sliding properties. The sliding ring needs to provide advantageous friction conditions. The bearing race as such, the basic member, needs to be able to withstand mechanical loads. In particular, it has to be produced from a material which, even under low temperature conditions, is impact-resistant.
In order to ensure that, when external forces act on the protective cone, the cone does not come into contact with the components of the double universal joint contained therein, the bearing race or its basic member includes a projection. The projection projects towards the first axial end. Under normal operating conditions, the folds do not come into contact with the projection. Contact can only be established if the protective cone is subjected to an external force or is loaded in partial regions if the articulation angle is particularly high. If a projection is provided to ensure that the guiding ring and the protective cone can be moved without coming into contact with the bearing race, the rotational diameter of the projection is smaller than the diameter of the first opening of the guiding ring.
From the following detailed description, taken in conjunction with the drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.